Device and Method for Qualitative and Quantitative Analysis of Heavy Metals Utilizing Rotary Disc System

ABSTRACT

The present invention relates to a device and a method for qualitative and quantitative analysis of heavy metals and more particularly provides a device and a method for qualitative and quantitative analysis of heavy metals utilizing a rotary disc system.

BACKGROUND OF THE INVENTION 1. Field of the Invention

This application claims priority to Korean Patent Application No.10-2017-0154395, filed on Nov. 20, 2017, and Korean Patent ApplicationNo. 10-2018-0053636, filed on May 10, 2018, the disclosures of which areincorporated herein by reference.

The present invention relates to a device and a method for qualitativeanalysis and quantitative analysis of heavy metals and, moreparticularly, to a device and a method for qualitative analysis andquantitative analysis of heavy metals using a rotatable disk system.

2. Description of the Related Art

In general, the most widely used method for detecting heavy metals isspectroscopic analysis such as inductively coupled plasma massspectrometry or atomic absorption/emission spectrometry. Massspectrometry and spectroscopy based heavy metal detection methods areaccurate and have high detection limits, but they are expensive andrequire skilled analytical techniques, making it difficult to perform aheavy metal analysis in the field quickly and simply.

It is required to develop economical and cost-effective colordevelopment based heavy metal analysis system for replacing expensivemass spectrometry and spectroscopy based heavy metal analysis equipment,and development of miniaturized analysis system that can be convenientlyapplied in the field is required. In addition, it is required to developa system capable of quantitative analysis as well as qualitativeanalysis of heavy metals while shortening analysis time by performingsimultaneous detection of multiple heavy metals.

In addition, it is required to facilitate the qualitative/quantitativeanalysis of heavy metals with the naked eyes by making the colordevelopment reaction between the organic ligand coated on a detectionunit and the heavy metal uniformly over the detection unit via moreuniform movement of a fluid sample when the fluid sample is developed inthe detection unit and by preventing the moisture condensationphenomenon in the detection unit. In addition, it is necessary toincrease the detection limit by making the color developed distancelonger so that the naked eyes can be identified by ensuring the colordeveloped distance beyond a certain level even at a low heavy metalconcentration.

SUMMARY OF THE INVENTION

The present invention pertains to a device for qualitative analysis andquantitative analysis comprising a rotatable platform and a plurality ofmicrofluidic structures disposed radially and symmetrically on therotatable platform. Each of the plurality of the microfluidic structurescomprises a top layer comprising a sample injection unit into which afluid sample containing heavy metals is injected and a microfluidicchannel (a siphon channel) which is a passage through which the samplecan be moved to a first detection unit and connects the sample injectionunit to the one end of the first detection unit; the first detectionunit coated with an organic substance capable of causing the colordevelopment reaction with heavy metals of the sample; and a bottom layerincluding a portion where the first detection unit is inserted and aruler for measuring the color developed distance. Each of the pluralityof the microfluidic structures may receive different kinds of samples.The rotation of the device is controlled so that the sample moves fromthe sample injection unit to the microfluidic channel and then to thefirst detection unit, and the qualitative analysis through the colordevelopment reaction of the heavy metals in the first detection unit andthe quantitative analysis through the measurement of the color developeddistance may be possible.

Further, the device for qualitative analysis and quantitative analysisaccording to the present invention further comprises an air circulationchannel connecting between the sample injection unit and the other endof the first detection unit, wherein the air circulation channel canincrease the rate of evaporation of the fluid sample in the firstdetection unit and prevent moisture condensation phenomenon in the firstdetection unit.

Further, the device for qualitative analysis and quantitative analysisaccording to the present invention comprises a reservoir area connectingthe microfluidic channel with the first detection unit, wherein one endof the first detection unit can be accommodated in the reserve area.

Further, the device for qualitative analysis and quantitative analysisaccording to the present invention may comprise a second detecting unithaving a width smaller than the width of the first detecting unitinstead of the first detecting unit.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the sample injection unitmay include a space capable of receiving the sample and an openingthrough which the sample can be injected.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the control of the rotationof the device can be accomplished by rotating the device firstly andthen stopping so that the sample injected into the sample injection unitis moved to the microfluidic channel; rotating the device secondarily sothat the sample moved to the microfluidic channel is moved to thereservoir area; and stopping the device so that sample moved to thereservoir area is developed in the first detection unit.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, one end of the sampleinjection unit and the detection unit are connected to the microfluidicchannel and the microfluidic channel may include a portion of a “U”shaped tube so that the sample can be received within the microfluidicchannel after the first rotation and before the second rotation of thedevice.

Also, in the device for qualitative analysis and quantitative analysisaccording to the present invention, the first rotation may be performedat 2000 to less than 4000 RPM for 5 to 20 seconds and the secondrotation may be performed at 4000 to 6000 RPM for 3 to 10 seconds.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the rotatable platform is acircular disk and may have a diameter of 12 cm to 20 cm.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the heavy metals that maybe included in the sample may comprise Fe²⁺, Zn²⁺, Hg²⁺, Cr⁶⁺, Ni²⁺, orCu²⁺.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the organic materialpreviously applied to the first detection unit may comprisedimethylglyoxime, bathophenanthroline, dithiooxamide, dithizone,diphenylcarbazide, or 1-(2-pyridylazo)-2-naphthol.

Further, the present invention pertains to an analytic method of a fluidsample containing heavy metals by using the qualitative analysis andquantitative analysis device according to the present invention. Theanalytic method comprises: (S1) injecting the sample into the sampleinjection unit; (S2) controlling the rotation of the device; and (S3)performing at least one of qualitative analysis and quantitativeanalysis of the sample developed in the detection unit.

Further, in the analytic method of a fluid sample containing heavymetals according to the present invention, the injection of the sampleinto the sample injection unit of the step (S1) may comprise injectingthe fluid sample containing different kinds of heavy metals into each ofthe plurality of microfluidic structures, or injecting the fluid samplecontaining same kinds of the heavy metals of varying concentrations intoeach of the plurality of microfluidic structures.

Further, in the analytic method of a fluid sample containing heavymetals according to the present invention, the controlling of therotation of the device of the step (S2) may comprise (S2-1) rotating thedevice firstly and then stopping so that the sample injected into thesample injection unit is moved to the microfluidic channel; (S2-2)rotating the device secondarily so that the sample moved to themicrofluidic channel is moved to the reservoir area; and (S2-3) stoppingthe rotation of the device so that the sample moved to the reservoirarea is developed in the detection unit.

Further, in the analytic method of a fluid sample containing heavymetals according to the present invention, the performance of at leastone of qualitative analysis and quantitative analysis of the sample ofthe step (S3) may comprise performing at least one of (S3-1) qualitativeanalysis through the color development reaction of the sample developedin the detection unit and (S3-2) the quantitative analysis through themeasurement of the color developed distance.

Effect of the Invention

According to the device for qualitative analysis and quantitativeanalysis (1, 1′) and the analysis method of the sample using the same(2) according to one embodiment of the present invention, the increaseof the detection limit of heavy metals through the control of theautomated fluidic control and the control of the torque and capillaryforce is possible. It is possible to improve the detection limit ofheavy metal ions by the torque control. That is, it is possible toimprove the detection limit by controlling the color developmentreaction time and the colored area via adjustment of the centrifugalforce and the capillary force by control of the rotation of the device.

According to the device for qualitative analysis and quantitativeanalysis (1, 1′) and the analysis method of the sample using the same(2) according to one embodiment of the present invention, qualitativeanalysis and quantitative analysis of several heavy metals can beperformed with one device (1, 1′). According to the present invention,economical and rapid multi-metal qualitative/quantitative analysis ispossible. It is more economical than conventional expensive spectroscopyor mass spectrometry based heavy metal detector and can shorten analysistime. In addition, the configurations for qualitative analysis andquantitative analysis can be integrated into one miniaturized device (1,1′), and can be applied quickly and conveniently in the field wherequalitative/quantitative analysis of heavy metals is required.

In addition, since the channel (a microfluidic channel) and thedetection unit are all patterned in one device, the fabrication of thedevice for qualitative analysis and quantitative analysis (1, 1′) issimple.

Further, according to the device for qualitative analysis andquantitative analysis (1, 1′) and the analysis method of the sampleusing the same (2) according to one embodiment of the present invention,by providing an air circulation channel, it is possible to prevent themoisture condensation phenomenon in the detection unit when the fluidsample is developed in the detection unit, thereby making it easy toidentify the color with the naked eyes and minimizing errors inanalysis. Further, by providing a reservoir area at the end of themicrofluidic channel and positioning one end of the detection unitwithin the reservoir area, the fluid sample moves more uniformly whenthe fluid sample is developed in the detection unit and the colordevelopment reaction between the organic ligand coated on the detectionunit and the heavy metals of the sample can be made more uniform.

Further, by narrowing the width of the detection unit, the colordeveloped distance becomes longer and the detection limit can beincreased. That is, since the naked eye can be identified by ensuringthe color developed distance beyond a certain level even at a low heavymetal concentration, by making the color developed distance longer, thesample can be detected even when the concentration of the heavy metal islower.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a device for qualitative analysis and quantitativeanalysis according to one embodiment of the present invention, and FIGS.1B and 1C show microfluidic structures of the device for qualitativeanalysis and quantitative analysis of FIG. 1A.

FIG. 2A illustrates a device for qualitative analysis and quantitativeanalysis according to another embodiment of the present invention, andFIGS. 2B and 2C show microfluidic structures of the device forqualitative analysis and quantitative analysis of FIG. 2A.

FIGS. 3A to 3D show each layer of a rotatable platform comprisingmicrofluidic structures.

FIG. 4 shows an example of a color development reaction between heavymetals ions and organic complexing agents.

FIG. 5 shows an example of simultaneous qualitative analysis of heavymetals using the device for qualitative analysis and quantitativeanalysis according to the present invention.

FIGS. 6A and 6B show examples of quantitative analysis of heavy metalsusing the device for qualitative analysis and quantitative analysisaccording to the present invention.

FIG. 7 shows the results of the development of the sample at eachdetector of the devices for qualitative analysis and quantitativeanalysis of FIGS. 1A and 2A.

FIG. 8 shows a flowchart of a method of analyzing a sample using thedevice for qualitative analysis and quantitative analysis according tothe present invention.

FIG. 9 shows a system for qualitative analysis and quantitative analysisthat includes and can rotate the device for qualitative analysis andquantitative analysis according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the device for qualitative analysis and quantitative analysiscomprising a rotatable platform and a plurality of microfluidicstructures disposed radially and symmetrically on the rotatable platformaccording to present invention, each of the plurality of microfluidicstructures comprises a top layer comprising a sample injection unit intowhich a fluid sample containing heavy metals is injected and amicrofluidic channel which is a passage through which the sample can bemoved to a first detection unit and connects the sample injection unitto the one end of the first detection unit; the first detection unitcoated with an organic substance capable of causing the colordevelopment reaction with heavy metals of the sample; and a bottom layerincluding a portion where the first detection unit is inserted and aruler for measuring the color developed distance. Each of the pluralityof the microfluidic structures may receive different kinds of samples.The rotation of the device is controlled so that the sample moves fromthe sample injection unit to the microfluidic channel and then to thefirst detection unit, and the qualitative analysis through the colordevelopment reaction of the heavy metals in the first detection unit andthe quantitative analysis through the measurement of the color developeddistance may be possible.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, it further may comprise anair circulation channel connecting between the sample injection unit andthe other end of the first detection unit, wherein the air circulationchannel can increase the rate of evaporation of the fluid sample in thefirst detection unit and prevent moisture condensation phenomenon in thefirst detection unit.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, it may comprise a reservoirarea connecting the microfluidic channel with the first detection unit,wherein one end of the first detection unit may be accommodated in thereserve area.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, it may comprise a seconddetecting unit having a width smaller than the width of the firstdetection unit instead of the first detection unit.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the sample injection unitmay include a space capable of receiving the sample and an openingthrough which the sample can be injected.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the control of the rotationof the device can be accomplished by rotating the device firstly andthen stopping so that the sample injected into the sample injection unitis moved to the microfluidic channel; rotating the device secondarily sothat the sample moved to the microfluidic channel is moved to thereservoir area; and stopping the device so that sample moved to thereservoir area is developed in the first detection unit.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, one end of the sampleinjection unit and the detection unit are connected to the microfluidicchannel and the microfluidic channel may include a portion of a “U”shaped tube so that the sample may be received within the microfluidicchannel after the first rotation and before the second rotation of thedevice.

Also, in the device for qualitative analysis and quantitative analysisaccording to the present invention, the first rotation may be performedat 3000 RPM for 10 seconds, the second rotation may be performed at 5000RPM for 5 seconds.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the rotatable platform is acircular disk and may have a diameter of 12 cm to 20 cm.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the heavy metals that maybe included in the sample may be Fe²⁺, Zn²⁺, Hg²⁺, Cr²⁺, Ni²⁺, or Cu²⁺.

Further, in the device for qualitative analysis and quantitativeanalysis according to the present invention, the organic materialpreviously applied to the first detection unit may comprisedimethylglyoxime, bathophenanthroline, dithiooxamide, dithizone,diphenylcarbazide, or 1-(2-pyridylazo)-2-naphthol.

Further, in the analytic method of a fluid sample containing heavymetals by using the qualitative analysis and quantitative analysisdevice according to the present invention, the method comprises: (S1)injecting the sample into the sample injection unit; (S2) controllingthe rotation of the device; and (S3) performing at least one ofqualitative analysis and quantitative analysis of the sample developedin the detection unit.

Further, in the analytic method of a fluid sample containing heavymetals according to the present invention, the injection of the sampleinto the sample injection unit of the step (S1) may comprise injectingfluid sample containing different kinds of the heavy metals into each ofthe plurality of microfluidic structures, or injecting fluid samplecontaining same kinds of heavy metals of varying concentrations intoeach of the plurality of microfluidic structures.

Further, in the analytic method of a fluid sample containing heavymetals according to the present invention, the controlling of therotation of the device of the step (S2) may comprise (S2-1) rotating thedevice firstly and then stopping so that the sample injected into thesample injection unit is moved to the microfluidic channel; (S2-2)rotating the device secondarily so that the sample moved to themicrofluidic channel is moved to the reservoir area; and (S2-3) stoppingthe rotation of the device so that the sample moved to the reservoirarea is developed in the detection unit.

Further, in the analytic method of a fluid sample containing heavymetals according to the present invention, the performance of at leastone of qualitative analysis and quantitative analysis of the sample ofthe step (S3) may comprise performing at least one of (S3-1) qualitativeanalysis through the color development reaction developed in thedetection unit and (S3-2) the quantitative analysis through themeasurement of the color developed distance.

Hereinafter, the device and the method for qualitative analysis andquantitative analysis of heavy metals using a rotatable disk systemaccording to the present invention will be described in detail. Theaccompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate embodiments of the presentinvention and the technical scope of the present invention is notlimited thereto.

In addition, the same or corresponding components are denoted by thesame reference numbers regardless of the figures, and redundantdescription thereof will be omitted. For convenience of explanation, thesize and shape of each constituent member shown may be exaggerated orreduced.

FIG. 1A shows a device for qualitative analysis and quantitativeanalysis (1) according to one embodiment of the present invention, andFIG. 1B shows microfluidic structures (20) of the rotatable disk systemof FIG. 1A.

First, referring FIG. 1A, the device for qualitative analysis andquantitative analysis (1) includes the rotatable platform (10) and aplurality of the microfluidic structures (20) provided on the rotatableplatform (10). The rotatable platform (10) may be, for example, acircular disk, and the size may be, for example, in one embodiment, 12cm to 20 cm in diameter, and in another embodiment, less than 12 cm indiameter.

The rotatable platform (10) includes the plurality of microfluidicstructures (20) which are positioned radially and symmetrically on therotatable platform (10). For example, the plurality of microfluidicstructures (20) may comprise two, four, six, eight, ten, or twelve ofthe structures. In FIG. 1A, six microfluidic structures (20) are showndisposed on the rotatable platform (10).

Referring to FIG. 1B, each microfluidic structure (20) of the pluralityof microfluidic structures (20) is shown. The microfluidic structures(20) include a top layer (see FIG. 3B), a detection unit (120) coatedwith an organic substance capable of causing a color developmentreaction with the heavy metals in a fluid sample, and a bottom layer(see FIG. 3D). The top layer includes a sample injection unit (100) intowhich a fluid sample containing heavy metals is injected and amicrofluidic channel (110) through which the fluid sample can move tothe detection unit. The bottom layer includes a portion where the firstdetection unit (120) can be inserted (see FIG. 3D) and a ruler (130) formeasuring the color developed distance.

Each microfluidic structure (20) of the plurality of the microfluidicstructures (20) may receive the fluid sample containing different kindsof the heavy metals. The heavy metals that may be included in the fluidsample may include, for example, Fe²⁺, Zn²⁺, Hg²⁺, Cr⁶⁺, Ni²⁺, or Cu²⁺.

The sample injection unit (100) includes a space for accommodating afluid sample containing the heavy metals and an opening (100 a) throughwhich the fluid sample can be injected into the space. The sampleinjection unit (100) and one end of the first detection unit (120) maybe connected to the microfluidic channel (110). Further, the sampleinjection unit (100) may include a blocking unit (100 b) which preventsthe sample injected through the opening (100 a) from flowing directlyinto the microfluidic channel (110) and stores the sample in the innerspace of the sample injection unit (100) by using drop of the channel.Since the vicinity of the rear end portion (100 c) of the sampleinjection unit (100) where the sample injection unit (100) and themicrofluidic channel (110) are connected to each other in the sampleinjection unit (100) has, for example, a streamlined shape, when thefluid sample injected into the injection unit (100) moves to themicrofluidic channel (110), the resistance of the fluid sample isminimized and all of the fluid sample injected into the sample injectionunit (100) is moved to the microfluidic channel (110).

The microfluidic channel (110) may have a width of 1 mm and a depth of100 μm. The microfluidic channel (110) may comprise, for example, aportion of a “U” shaped tube. As will be described below, the fluidsample including heavy metals after the first rotation and before thesecond rotation of the device for qualitative analysis and quantitativeanalysis (1) has the passage through which the fluid sample moves due tothe hydrophilicity of the microfluidic channel (110), and as a result,the fluid sample can be accommodated in the microfluidic channel (110).

The first detection unit (120) may be coated with an organic materialcapable of causing a color development reaction with heavy metals of thefluid sample so that the fluid sample can be developed. The firstdetection unit (120) may be made of a porous hydrophilic material, forexample, paper, nitrocellulose, cotton, silica based sol-gel matrix,etc., and may be preferably made of paper.

The ruler (130) is positioned alongside of the first detection unit(120) in the vicinity of the first detection unit (120). The ruler (130)may be, for example, scaled in millimeters (mm). Alternatively, it maybe scaled in units of concentration such as ppm, ppb, etc., in additionto the length unit such as mm in the scale unit (130). In the case wherethe scale is expressed in terms of the concentration unit in the ruler(130), it may be expressed in terms of a concentration unit obtained bysubstituting the development distance of the heavy metals into acalibration curve (see FIGS. 6A and 6B).

The device for qualitative analysis and quantitative analysis (1) alsoincludes an air circulation channel (140). The air circulation channel(140) connects between the sample injection unit (100) and the other endof the first detection unit (120). Due to this, the sample injectionunit (100), the microfluidic channel (110), the first detection unit(120), the air circulation channel (140), and the sample injection unit(100) are connected to be circulated in order. By introducing the aircirculation channel (140), the evaporation rate of the fluid sample ofthe first detection unit (120) is increased, and the moisturecondensation phenomenon in the first detection unit (120) is prevented.On the other hand, with respect to the sample injection unit (100),since the air circulation channel (140) is located at the center of thecircular disk-shaped rotatable platform (10) and the microfluidicchannel (110) is positioned toward the edge of the rotatable platform(10), when the rotatable platform (10) rotates, the sample of the sampleinjection unit (100) moves to the microfluidic channel (110) by thecentrifugal force and does not move to the air circulation channel(140). Additionally, in order to prevent the possibility of movement, ahole having a depth of about 1 mm and a diameter of about 0.8 mm isdrilled at a point where the sample injection unit (100) and the aircirculation channel (140) are connected to each other to form acapillary valve operated by an air pressure, thereby preventing thesample from moving from the sample injection unit (100) to the aircirculating channel (140).

The device for qualitative analysis and quantitative analysis (1)further includes a reservoir area (150) at the location where themicrofluidic channel (110) is connected to the first detection unit(120), and one end of the first detection unit (120) is accommodated inthe reservoir area (150). The reservoir area (150) is a recessedpatterned area in each of the top and bottom layers (see FIG. 3A) of therotatable platform (10) so that the fluid sample can be receivedtherein. The fluid sample accommodated in the microfluidic channel (110)during the first rotation of the rotatable platform (10) moves from themicrofluidic channel (110) to the reservoir region (150) during thesecond rotation of the rotatable platform (10) and then is stored (I.e.,trapped) in the reservoir area (150) without being developed into thefirst detection unit (120) by the centrifugal force due to the rotation.When the second rotation of the rotatable platform (10) is stopped, thefluid sample is developed into the first detection unit (120) connectedto the reservoir area (150). A more detailed description thereof will begiven below with reference to FIG. 8.

One end of the first detection unit (120) is accommodated in thereservoir region (150), while the fluid sample is injected from themicrofluidic channel (110) located in the top layer of the rotatableplatform (10) to one end of the first detection unit (120′) insertedinto the bottom layer of the rotatable platform (10), that is, downward.Therefore, the fluid sample can be developed more uniformly in the firstdetection unit (120).

FIG. 1C shows exemplary dimensions of the microfluidic structures (20)of the rotatable disk system of FIG. 1B. Exemplary dimensions of themicrofluidic structures (20) are not limited to those shown in FIG. 1C,but may be modified or changed according to various environmentsembodied in the present invention.

FIG. 2A shows a device for qualitative analysis and quantitativeanalysis (1′) according to another embodiment of the present invention,and FIG. 2B shows the microfluidic structures (20′) of the rotatabledisk system of FIG. 2A. The device for qualitative analysis andquantitative analysis (1′) of FIG. 2A, like the device for qualitativeanalysis and quantitative analysis (1) of FIG. 1A, comprises therotatable platform (10) and a plurality of the microfluidic structures(20′) provided in and the rotatable platform (10). The top layer of therotatable platform (10) includes the sample injection unit (100) intowhich a fluid sample containing heavy metals is injected and themicrofluidic channel (110) which is a passage through which the fluidsample can move to the detection unit. The bottom layer includes aportion where the detection unit (120′) can be inserted (see FIG. 3D)and the ruler (130) for measuring the color developed distance.

In FIGS. 2A and 2B, the width of the second detection unit (120′) issmaller than the width of the first detection unit (120) in FIGS. 1A and1B. Accordingly, in the second detection unit (120′), the colordeveloped distance is longer than that of the first detection unit(120), and thus the detection limit increases. In this connection,reference is made to the experimental results shown in FIG. 7. FIG. 7shows the experimental results regarding the color developed distance,wherein when the width of the second detection unit (120′) is reduced to50% of the first detection unit (120) (for example, when the length ofthe first detection unit (120) is 60 mm and the width is 5 mm, and whenthe second detection unit (120′) has a length of 60 mm and a width of2.5 mm), the concentration of each heavy metal in the sample is 100 ppm.

For example, when the width of the second detection unit (120′) is 50%smaller than the width of the first detection unit (120), the colordeveloped length can be increased by about 20 to 50% and the detectionlimit can be doubled.

FIG. 2C illustrates exemplary dimensions of the microfluidic structures(20) of the rotatable disk system of FIG. 2B.

In the description of the device for qualitative analysis andquantitative analysis (1′) of FIG. 2A and the microfluidic structures(20′) of FIG. 2B, the description of the components that overlap withthose in the device for qualitative analysis and quantitative analysis(1) of FIG. 1A and the microfluidic structures (20) of FIG. 1B refers tothe descriptions of FIGS. 1A and 1B.

FIGS. 3A to 3D illustrate each layer of the rotatable platform (10)comprising the microfluidic structures (20) of FIG. 1A. As shown in FIG.3A, the rotatable platform (10) including the microfluidic structures(20) is mainly composed of three layers, each of which corresponds tothe top layer wherein the sample injection unit (100) and themicrofluidic channel (110) are positioned (see FIG. 3B), a bottom layer(see FIG. 3D) for inserting the detection unit, and a PSA (Pressuresensitive adhesion) layer (see FIG. 3C) for bonding the top and bottomlayers. The materials of the top and bottom layers may include, forexample, polycarbonate (PC), polymethyl methacrylate (PMMA) and thelike. The sample injection unit (100) and the microfluidic channel (110)are provided within the top layer, and the sample injection unit (100)and the microfluidic channel (110) can be formed through a patterningprocess using micro-milling. The lower surface of the top layer wherethe first and second detection units (120, 120′) are positioned may bevariously modified and changed so that the first and second detectionunits (120, 120′) can be inserted, including a concave portion inconformity with the shape of the first and second detection units (120,120′). Also, the depth of the concave portion can be variously modifiedand changed according to the environment in which the present inventionis actually implemented. A hydrophilic material is coated on the insideof the microfluidic channel (110) to receive the fluid sample containingthe heavy metals. A space in which the first and second detection units(120, 120′) can be inserted is provided and the ruler (130) is patternedin the bottom layer. Since the space in which the first and seconddetection units (120, 120′) can be inserted is provided in the bottomlayer, the fluid sample is supplied from the sample injection unit (100)and the microfluidic channel (110) provided in the top layer to thefirst and second detection units (120, 120′). Since the fluid sampleflows downward to the first and second detection units (120, 120′), thefluid sample is more uniformly developed from the one end of the firstand second detection units (120, 120′) than in the case where themicrofluidic channel (110) and the first and second detection units(120, 120′) are positioned in the same layer. The PSA layer is anadhesive layer serving to bond the top layer and the bottom layer, andcan be formed into, for example, an acryl based double-sided adhesivetape. In a tape or a plate having an adhesive component corresponding tothe size of the rotatable platform (10), the region corresponding to thesample injection unit (100) and the microfluidic channel (110) in thetop layer, and the region corresponding to the first and seconddetection units (120, 120′) in the bottom layer may be removed bycutting or the like, as shown in FIG. 3C. On the other hand, the toplayer and the PSA layer are made of a transparent material so that thedevelopment of the sample in the detection unit (120) and the ruler(130) in the bottom layer can be identified. However, the presentinvention is not limited to the above-described embodiments, and variousmodifications and changes are possible, for example, the ruler (130) maybe patterned on the top layer.

According to the device for qualitative analysis and quantitativeanalysis (1, 1′) of the present invention, the rotation of the devicefor qualitative analysis and quantitative analysis (1) is controlled sothat the fluid sample containing the heavy metals moves from the sampleinjecting unit (100) into the microfluidic channel (110), and then movesto the first and second detection units (120, 120′). For example, afterthe fluid sample containing heavy metals is injected into the sampleinjection unit (100), when the device for qualitative analysis andquantitative analysis (1, 1′) is first rotated for 10 seconds at 3000RPM and then stopped, the fluid sample containing the heavy metals movesto the microfluidic channel (110). When the device for qualitativeanalysis and quantitative analysis (1, 1′) is secondarily rotated at5,000 RPM for 5 seconds, the fluid sample containing the heavy metals inthe microfluidic channel (110) of the top layer is injected to thereservoir area (150) inserted in the bottom layer by the centrifugalforce. When the rotation of the device for qualitative analysis andquantitative analysis (1, 1′) is stopped, the fluid sample containingheavy metals is developed on the first and second detection units (120,120′) by the capillary force.

The fluid sample including the heavy metals developed on the detectionunit (120, 120′) reacts with the reagents previously coated on thedetection unit (120, 120′) to indicate colors related to the heavymetals. As an organic substance that can be previously applied to thedetection unit (120, 120′), for example, an organic chelating agent maybe used. In one embodiment, organic substances based on a reaction listbetween heavy metal ions and the organic chelating agents as shown inTable 1 below may be used.

TABLE 1 Heavy Metals Form Chelating agent (concentration) Nickel (Ni²⁺)Sulfate Dimethylglyoxime (100 mM) Iron (Fe²⁺) SulfateBathophenanthroline (5 mM) Copper (Cu²⁺) Sulfate Dithiooxamide (20 mM)Mercury (Hg²⁺) Sulfate Dithizone (5 mM) Chromium (Cr⁶⁺) OxideDiphenylcarbazide (10 mM) Zinc (Zn²⁺) Sulfate1-(2-Pyridylazo)-2-naphthol (5 mM)

FIG. 4 shows the color development reaction between heavy metal ions andthe organic chelating agents according to Table 1. In the embodiment ofFIG. 4, PAN (1-(2-pyridylazo)-2-naphthol), Bphen (bathophenanthroline),DMG (dimethylglyoxime), DTO (dithiooxamide), DCB (diphenylcarbazide) andDTZ (dithizone) were used as the organic chelating agents. And 1% H₂SO₄was added to DCB for Cr⁶⁺ to improve the reaction selectivity of Cr⁶⁺ion for DCB and the color development reaction.

The device for qualitative analysis and quantitative analysis (1, 1′)according to the present invention can provide a simultaneousqualitative analysis up to a level of 25 ppm for a plurality of heavymetals such as Fe²⁺, Zn²⁺, Hg²⁺, Cr⁶⁺, Ni²⁺, or Cu²⁺ within 15 minutes.

FIG. 5 shows an example of a simultaneous qualitative analysis for sixheavy metals (100 ppm) using the device for qualitative analysis andquantitative analysis (1) of FIG. 1A. The qualitative analysis can beperformed on the heavy metals contained in the fluid sample with the hueaccording to the color development reaction on the first and seconddetection unit (120, 120′). For example, when the hue according to thecolor development reaction of the fluid sample is observed with thenaked eyes, it is possible to identify the kind of the heavy metalscontained in the sample.

In addition, the degree of development of the fluid sample including theheavy metals on the first and second detection unit (120, 120′) can bequantitatively analyzed by using the ruler (130). Referring to theexample of FIG. 5, it can be seen that the degree of development of thefluid sample including heavy metals on the detection unit (120′) of eachof the plurality of microfluidic structures (20) is different from eachother. It is possible to measure the extent to which a fluid samplecontaining the heavy metals is developed by using the ruler (130). Thedevelopment distance of the corresponding fluid sample on the detectionunit (120) is measured using the respective ruler (130), the types ofheavy metals contained in the fluid sample are determined by the abovequalitative analysis, and the quantitative analysis of the heavy metalscan be performed by substituting the development distance into acalibration curve for the heavy metals (see FIGS. 6A and 6B). As oneexample of quantitative analysis, FIG. 6A shows a case where Cr⁶⁺ isquantitatively analyzed and FIG. 6B shows a case where Fe²⁺ isquantitatively analyzed using the device for qualitative analysis andquantitative analysis (1) of FIG. 1A. For example, the numbers of 1 ppm,5 ppm, 10 ppm, 25 ppm, 50 ppm, and 100 ppm described in FIG. 6A are theresults of quantitative analysis of Cr⁶⁺. This is a method in which thedegree of purple development corresponding to Cr⁶⁺ on the six detectionunits (120) is measured using the ruler (130) and then the measureddevelopment distance is substituted into the calibration curve of Cr⁶⁺to obtain the concentration on the x axis corresponding to the degree ofdevelopment on the y axis of the calibration curve so as that thequantitative analysis of Cr⁶⁺ can be performed. In the case of Fe²⁺ inFIG. 6B, the quantitative analysis can be performed in the same manner.At this time, in the case of Cr⁶⁺, the detection limit of thequalitative analysis is 1 ppm and the detection limit of thequantitative analysis is 5 ppm. In the case of Fe²⁺, the detection limitof the qualitative analysis is 25 ppm and the detection limit of thequantitative analysis is 50 ppm.

Hereinafter, with reference to FIG. 8, a method (2) of analyzing a fluidsample containing the heavy metals using the device for qualitativeanalysis and quantitative analysis (1, 1′) according to one embodimentof the present invention will be described. The steps of the method foranalyzing a sample (2) according to an embodiment of the presentinvention are as follows:

Step 1: Injecting a fluid sample into the sample injection unit (100) ofthe device for qualitative analysis and quantitative analysis (1, 1′)(S1);

Step 2: Controlling the rotation of the device for qualitative analysisand quantitative analysis (1, 1′) (S2); and

Step 3: Performing at least one of qualitative analysis and quantitativeanalysis (S3).

Step 1: Injecting a Fluid Sample into the Sample Injection Unit (100) ofthe Device for Qualitative Analysis and Quantitative Analysis (1, 1′)(S1)

The fluid sample is injected into each sample injection unit (100) ofthe plurality of the microfluidic structures (20) of the device forqualitative analysis and quantitative analysis (1, 1′). For example,about 40 μl of the fluid sample each can be injected into each sampleinjection unit (100). However, the present invention is not limited tothis embodiment, and the amount of the injection can be variouslyadjusted according to various environments in which the presentinvention is implemented. The fluid sample containing different kinds ofthe heavy metals is respectively injected into each of the plurality ofthe microfluidic structures (20, 20′) (S1-1) to perform qualitativeanalysis and/or quantitative analysis as described below, the fluidsample containing the same kind of the heavy metals of varyingconcentrations are respectively injected into each of the microfluidicstructures (20, 20′) (S1-2) to perform qualitative analysis and/orquantitative analysis as described below.

Step 2: Controlling the Rotation of the Device for Qualitative Analysisand Quantitative Analysis (1, 1′) (S2)

The device for qualitative analysis and quantitative analysis (1, 1′) ismounted on a system for qualitative analysis and quantitative analysis(3) capable of rotating the device for qualitative analysis andquantitative analysis (1, 1′), for example, a rotatable system forqualitative analysis and quantitative analysis (3) as shown in FIG. 9,and the device for qualitative analysis and quantitative analysis (1,1′) is rotated. This step (S2) includes the following detailed steps:

Step 2-1: The device for qualitative analysis and quantitative analysis(1, 1′) is initially rotated at 2000 to less than 4000 RPM for 5 to 20seconds and then is stopped to move the fluid sample including heavymetals injected into the sample injection unit (100) located at the toplayer of the microfluidic structure (20, 20′) to the microfluidicchannel (110) (S2-1).

Step 2-2: The device for qualitative analysis and quantitative analysis(1, 1′) is secondarily rotated at 4000 to 6000 RPM for 3 to 10 secondsto flow the fluid sample including heavy metals transferred to themicrofluidic channel (110) at step 2-1 into the reservoir region (150)of the microfluidic structures (20, 20′) (S2-2).

Step 2-3: The rotation of the device for qualitative analysis andquantitative analysis (1, 1′) is stopped so that the fluid sampleincluding the heavy metals are guided by the capillary force from thereservoir region (150) to one end of the detection unit (120, 120′)accommodated in the reservoir region (150) to be developed on thedetection unit (120, 120′) (S2-3).

Step 3: Performing at Least One of Qualitative Analysis and QuantitativeAnalysis (S3)

A qualitative analysis can be performed on the fluid sample developed onthe detection unit (120, 120′) by a method of analyzing the colordevelopment reaction on the detection unit (120, 120′) with the nakedeyes (S3-1), or a quantitative analysis can be performed by measuringthe degree of development of the fluid sample developed on the detectionunit (120, 120′) by using a ruler (130) and then substituting themeasured values to the calibration curves of the corresponding heavymetals developed on the scale (S3-2), or both of the quantitativeanalysis and the quantitative analysis can be performed (S3-1 and S3-2).Examples related to this are described above with reference to FIGS. 5,6A and 6B.

In summary, the device for qualitative analysis and quantitativeanalysis (1, 1′) according to an embodiment of the present inventionincludes the microfluidic structures (20) having the same structure thatcan detect a plurality of types (for example, six kinds) of heavy metalson a rotatable platform (10) (for example, a circular disk), whereineach microfluidic structure (20) is arranged radially and symmetricallyalong the rotational direction of the rotatable platform (10) andcomprises the detection unit (120, 120′) coated with an organicsubstance that can cause a color development reaction with the heavymetals.

According to the device for qualitative analysis and quantitativeanalysis (1, 1′) and the method of analyzing the sample using the same(2) according to the embodiment of the present invention, thecentrifugal force generated upon rotation of the device for qualitativeanalysis and quantitative analysis (1, 1′) can move the fluid samplecontaining the heavy metals to the detection unit (120, 120′) and thequalitative analysis can be performed through the color developmentreaction. Further, the fluid can be developed by the paper capillaryforce when the rotation of the device stops and the quantification maybe performed by identifying the color developed distance with the ruler(130) patterned on the device for qualitative analysis and quantitativeanalysis (1, 1′). It is possible to increase the detection limit ofheavy metals through automatic fluid control and control of torque andcapillary force. It is possible to improve the detection limit of heavymetal ions by the torque control. That is, by adjusting the centrifugalforce and the capillary force by the rotation control, it is possible toimprove the detection limit by controlling the reaction time of colordevelopment and the colored area. Specifically, when the developmentspeed of the sample containing heavy metals due to the capillary forcebecomes faster than the speed at which the heavy metals and the organicchelating agent react with each other on the detection unit, the samplecontaining the heavy metals fails to sufficiently react with the organicchelating agent and develops on the entire detection unit. In the caseof a heavy metal sample having a high concentration, there is no problemin detection because of the color appears, but there is a possibilitythat the quantitative property is lowered. In the case of a heavy metalsample of low concentration, there is a possibility that the colordevelopment does not occur due to insufficient reaction with the organicchelating agent of the detection unit, and the detection sensitivity andlimitations may be lowered. However, according to the present invention,since the centrifugal force acts on the opposite side of the capillaryforce, the centrifugal force is applied to control the solutiondevelopment speed by the capillary force so that the color developmentreaction can be sufficiently performed on the detection unit to improvethe detection limitations.

Further, according to the device for qualitative analysis andquantitative analysis (1, 1′) and the method of analyzing the sampleusing the same (2) according to the embodiment of the present invention,it is economical and quick in the qualitative/quantitative analysis ofmultiple heavy metals. It is more economical than conventional expensivespectroscopy or mass spectrometry based heavy metal detector and canshorten analysis time. Thus, it can be applied quickly and convenientlyin the field where the qualitative/quantitative analysis of heavy metalsis required.

The technical constitution of the present invention as described abovewill be understood by those skilled in the art that various changes inform and details may be made therein without departing from the spiritand scope of the invention. It is therefore to be understood that theabove-described embodiments are illustrative in all aspects and notrestrictive. In addition, the scope of the present invention isindicated by the appended claims rather than the detailed description ofthe invention. Also, all changes or modifications derived from themeaning and scope of the claims and their equivalents should beconstrued as being included within the scope of the present invention.

EXPLANATION OF REFERENCE NUMBERS

-   -   1, 1′: Device for qualitative analysis and quantitative analysis    -   2: Method of analyzing a sample    -   3: System for qualitative analysis and quantitative analysis    -   10: Rotatable platform    -   20, 20′: Microfluidic structure    -   100: Sample injection unit    -   110: Microfluidic channel    -   120, 120′: Detection unit    -   130: Ruler    -   140: Air circulation channel    -   150: Reservoir area

1. A device for qualitative analysis and quantitative analysiscomprising a rotatable platform and a plurality of microfluidicstructures disposed radially and symmetrically on the rotatableplatform, wherein each of the plurality of the microfluidic structurescomprises: a top layer comprising a sample injection unit configured toreceive an injection of a respective fluid sample containing heavymetals and a microfluidic siphon channel which is a passage providingfluid communication between the sample injection unit and one end of afirst detection unit; the first detection unit coated with an organicsubstance configured to produce a color development reaction with theheavy metals of the fluid sample; and a bottom layer including a portioninto which the first detection unit is inserted and a ruler configuredto measure a color developed distance of the color development reaction,wherein each of the plurality of the microfluidic structures isconfigured to receive a different kind of the respective fluid samplesthan other ones of the plurality of the microfluidic structures, whereinthe device is configured to move the respective fluid samples moves fromthe respective sample injection unit to the respective microfluidicchannel and then to the respective first detection unit when therotatable platform is rotated, and wherein the device is configured toprovide a qualitative analysis of the fluid samples through therespective color development reaction of the heavy metals in therespective first detection unit and the device is configured to providea quantitative analysis of the fluid samples through measurement of therespective color developed distances.
 2. The device according to claim1, further comprising a respective air circulation channel connectingeach sample injection unit and another end of each respective firstdetection unit, wherein each air circulation channel is configured toincrease a rate of evaporation of the fluid sample in the respectivefirst detection unit and is configured to prevent a moisturecondensation phenomenon in the respective first detection unit.
 3. Thedevice according to claim 1, further comprising a respective reservoirarea connecting each microfluidic channel with each respective firstdetection unit, wherein the one end of the respective first detectionunit is accommodated in the respective reservoir area.
 4. The deviceaccording to claim 1, further comprising a respective second detectingunit having a width smaller than a width of each respective firstdetecting unit.
 5. The device according to claim 3, wherein the deviceis configured to move the respective fluid samples by: a first rotationof the rotatable platform and then stopping the first rotation so thatthe fluid sample injected into each respective sample injection unit ismoved to the respective microfluidic channel; a second rotation of therotatable platform so that the fluid sample moved to each respectivemicrofluidic channel is moved to the respective reservoir area; andstopping rotation of the rotatable platform so that the fluid samplemoved to each respective reservoir area is developed in the firstdetection unit.
 6. The device according to claim 5, wherein eachmicrofluidic channel includes a portion of a “U” shaped tube that isconfigured to receive the respective fluid sample after the firstrotation and before the second rotation of the rotatable platform. 7.The device according to claim 5, wherein the first rotation of therotatable platform is performed at 2000 to less than 4000 RPM for 5 to20 seconds and the second rotation of the rotatable platform isperformed at 4000 to 6000 RPM for 3 to 10 seconds.
 8. The deviceaccording to claim 1, wherein the rotatable platform is a circular diskhaving a diameter of 12 cm to 20 cm.
 9. The device according to claim 1,wherein the heavy metals included in each of the fluid samples compriseFe²⁺, Zn²⁺, Hg²⁺, Cr⁶⁺, Ni²⁺, or Cu²⁺.
 10. The device according to claim9, wherein the organic substance that coats the first detection unitscomprises dimethylglyoxime, bathophenanthroline, dithiooxamide,dithizone, diphenylcarbazide, or 1-(2-pyridylazo)-2-naphthol.
 11. Amethod of analyzing the fluid samples by using the device according toclaim 1, the method comprising: injecting each fluid sample into therespective sample injection unit; rotating the rotatable platform; andperforming at least one of the qualitative analysis and the quantitativeanalysis of the fluid sample developed in each respective detectionunit.
 12. The method according to claim 11, wherein the injecting ofeach fluid sample into the respective sample injection unit comprises:injecting a first amount of each fluid sample into the respective one ofthe microfluidic structures; or injecting a second amount of each fluidsample into the respective one of the microfluidic structures, the firstamount of each fluid sample having a different concentration than thesecond amount of each fluid sample.
 13. A method of analyzing the fluidsamples by using the device according to claim 3, the method comprising:injecting each fluid sample into the respective sample injection unit;rotating the rotatable platform; and performing at least one of thequalitative analysis and the quantitative analysis of the fluid sampledeveloped in each respective detection unit, wherein the rotating of therotatable platform comprises: rotating the rotatable platform firstlyand then stopping the rotating so that the fluid sample injected intoeach respective sample injection unit is moved to the respectivemicrofluidic channel; rotating the rotatable platform secondarily sothat the fluid sample moved to each microfluidic channel is moved to therespective reservoir area; and stopping the rotation of the rotatableplatform so that the sample moved to each reservoir area is developed inthe respective detection unit.
 14. The method according to claim 11,wherein the performing of the at least one of the qualitative analysisand the quantitative analysis of each fluid sample comprises: performingthe at least one of the qualitative analysis through the colordevelopment reaction of each sample developed in the respectivedetection unit and the quantitative analysis through the measurement ofthe respective color developed distance.